investigation of isotropy of intra-event residuals of pgv and pgd using directional semivariogram

It is vital to consider spatial correlation of intensity measures in seismic assessment of spatially distributed lifeline systems. in recent years, various researches has been conducted to consider spatial correlation of intensity measures. previous studies using different intensity mesures proposed various models of spatial correlations. all these models are proposed under assumption of isotropy of intraevent residulas of intensity measures while garakaninezhad and bastami(2017) showed that this assumption is not acceptable for peak ground acceleration (pga) and spectral accelerations in different periods (sa). current study, investigates the assumption of isotropy of intraevent residuals of peak ground velocity (pgv) and peak ground displacement (pgd) using directional variogram method.